Conventional bead breaking machines, as is known, generally comprise a base, a wheel-carrier table mounted for rotation on the base, a column rising from the base and one or more arms for supporting tools, which can be mounting-demounting tools and/or one or more bead breaker rollers.
A bead breaker roller or tool is used for “bead breaking” or separating a tire from the edge of its respective rim, before proceeding with the actual disassembly of the tire, i.e. before forcing the tire to go beyond an edge of the rim for its extraction from the rim.
Tire mounting-demounting machines have already been proposed equipped with two bead breaker arms extending overhangingly from the column. Each arm supports a bead breaker roller, the bead breaker rollers being mounted for rotation at the head of respective arms so as to have opposing work fronts, i.e. directed against each other. In practice, once a tired wheel to be disassembled was placed and locked on the wheel-carrier table of a tire mounting-demounting machine, the extension/retraction and/or lowering/raising of the bead breaker arms is controlled so as to bring one bead breaker roller to one flank of the wheel and the other bead breaker roller to the other flank of the wheel. The wheel-carrier table is then rotated and a brief mutual approaching movement of the arms is simultaneously commanded; each bead breaker tool will then cause the progressive separation of the respective bead from the edge of the rim until the bead breaking at both flanks has been completed.
Tire mounting-demounting machines have already been proposed equipped with a single bead breaker arm, which after having bead broken one flank of a tire is moved to the opposite side of the wheel, i.e. to the other tire flank, in order to carry out the bead breaking also of the second flank of the tire.
As will be understood, conventional tire mounting-demounting machines are structurally complex and hence costly, and those with only one bead breaker arm involve rather long bead breaker times.
Patent documents, such as EP-0 838 354, EP-1 916 125, U.S. Pat. No. 4,047,553, EP-0 987 130, and EP-0 947 360 relate to mounting-dismounting machines including an arm supporting a pair of bead releasing rollers, which are designed to co-act or simultaneously engage, in use, a portion of a bead of a tired wheel to be bead released.